Prevention of caking of crystals, powders, and the like



l atented June 23 1931 PA TET En ALEXANDER CRUICKSEANK SCOTT, OF FAVEBSHAM, ENGLAND PREVENTION OF CAKING F CRYSTALS, POWDERS, AND THE LIKE No Drawing. Application filed November 3, 1928, Serial No. 317,120, and in Great Britain November 11, 1927.

cake in the presence of other vapours than that ofwater, such as hydrocarbon vapours. According to the present invention a method of'preventing caking in masses of crystalsor powders of the kind described consists in intimately incorporating with the 'said crystals or powders a proportion of fibrous material, for example, asbestos.

This invention further comprises improvements in or relating to explosives of the "-2 -type in which crystals of an oxygen carrying .salt,.such as potassium chlorate, ammonium nitrate or the like are employed.

.In the manufacture of explosive car Atridges from chlorates and the like difficulty A zn-is. frequently experienced on account of-the tendency of the crystals to cake together into ahard mass. Moreover, in the course of exploding such material in a long bore hole or other similar conditions the detonation 3 is not always perfect owing to the quenching .efiect ofthe potassium chlorideliberated in the combustion of potassium chlorate explosives,.which tends to interferevwith the combustion of the mass. If a potassium chlorate cartridge (impregnated in the ordi- "nary way .with fuel) be ignited without detonation, itwill be found that combustion proceeds irregularly and it is thought that a similar action may take place when "4.0 the cartridge is actually detonated in use. j However, this may be, the combustion fsuch cartridges is not always perfect. vIt is anobject of the present invention to overcome these. defects and difficulties.

According to the present invention a cartridge of the kind described contains, in-

timately distributed through the body of the crystals or. powder in the cartridge a small proportion of a fibrous material.

v The preferred fibrous material is asbestos but talc or mica can be I employed in admixture with asbestos.

The invention further includes a granular explosivethe grains whereof consist of oxygen carrying crystals of the kind described having intimately disseminated through their substances finely divided particles of an inert silicate of the kind set forth. Such granular explosive may be prepared by incorporating the oxygen carrying v crystals 3.

incorporation of a small quantity of fibrous material with solid nitro bodies, for example, tri-nitrotoluol (with or without the addition of other salts) for the purpose of pre- 1 venting caking of the cartridge.

When cartridges prepared as above de scribed are subsequently impregnated with liquid fuels evaporation of the fuel from the mass of explosive is greatly retarded. Moreover, the cartridge assumes only a slightly moist consistency considering the amount of liquid added. The liquid constituent does not subsequently exude or drain out and is not easilyexpressed' fromthe packet. Using 2% of asbestos up to 25% of fuel by volume has been added without subsequent exudation.

j The following are'examplesof cartridges manufactured in accordance with the pres- V 'ent invention 1 f" I Example I Potassium chlorate crystals are taken of the fineness ordinarily employed for chlorate cartridges or even somewhat coarser (i. e. capable ofpassing a screen having about .60 meshes per lineal inch) but preferably finer. These are mixed with a proportion of powdered asbestos fibre, say about 10% by.

weight of the crystals and are trituratedtogether until the whole mixture is uniform.

The resulting powder is thereafter incorporated by trituration in a further batch of chlorate crystals in the proportion of about;

10% of the whole so that the resulting material contains only about 1% of asbestos fibre. Trituration is continued until the average size of the particles of the material is in the neighbourhood of one five-hundredths of an inch in diameter or less. The product is packed into cartridges in the usual way, preferably under pressure, so as to obtain a cartridge as dense as possible. The pressure may be applied in an ordinary filling machine an if the were; of the fill,- ing machine be loaded so as to apply a suitable pressure to the material a density as high as 1.6 or over may be obtained in the space of the cartridge containing the crystals. Finally, the cartridge is impregnated with a liquid fuel. It is found that there is no tendency to cake or bind either'before or after impregnation of the cartridge with the fuel.

A cartridge manufactured in this manner will be found to burn quite uniformly, it remains soft and yielding over a considerable period and detonates better than cartridges of the usual kind.

Even if impregnated with nitro-bodies or admixed with solid nitro-bodies such as dinitro-toluol the cartridge remains soft during storage.

Example [I The procedure is'the same as in Example I with the followlng 1ngred1ents:

Solid bodies ground together:

Parts by weight Potassium chlorate 6,5. 5 Asbestos fibre 3 Sodium nitrate 30 Fuel:

Orthonitrotoluol 10 Kerosene 1 Castoroil 0.5

The liquid ingredients are used for impregnating the compressed cartridge.

Ewample l I 1 Solid ingredients: 7

Parts by weight Potassium chlorate -rs 93 Potasslum nltrate 5 Asbestos fibre; 2

Although the mass of the grains is pressed to a considerable density, the presence of the asbestos imparts a certain porosity to the grains which enables the product to absorb fuels.v Too great a pressure should not be used to press the mass or non-porous grains may result.

The wet mass from the mill may also be pressed into pellets. These are dried and impregnated with the necessary amount of fue In place of potassium nitrate, other soluble salts, such as sodium nitrate, sodium chloride and potassium chloride can be used as binding agents. With potassium perchlorate, ammonium nitrate can also be used.

Any suitable liquid fuel can be used to impregnate the grains, such as kerosene, nitroben'zene, nitro-toluol, etc. or mixtures of same.

Example I V The following is an example of preventing caking in abody other than an explosive charge As an example of this aspect of the invention may be mentioned the use of finely divided asbestos in admixture with fine crystals of sodium nitrate. The presence of about 1 to 5% of asbestos powder ground to such asize that the average diameter of the particles is-less than one five-hundredths of an inch, suffices to prevent binding of such a hygroscopic salt over apparently an indel nite period. In the application of this salt as a manure the invention provides the means to prevent binding and facilitate its more even distribution over the soil. Other manures may be treated in like manner and the invention comprises a manure or fertilizer consisting of crystals or powder of a fertilizing substance in admixture with a small proportion of an inert silicate such as is fibres not exceeding 5%.

I claim 1.'A -method of preventing caking of a crystalline masswhich consists in intimately incorporating with the said mass a proportion of asbestos fibre not exceedingr5%.

' 2. A method of preventing caking of a crystalline mass which consists in tr-iturating with the said mass a proportion of asbestos fihrees not exceeding 5%. Y

3. A method of preventing caking of a crystalline mass which consists in intimatelyincorporating with the said mass approxi- -mately 1% of asbestos fibres.

4. A method of preventing caking of a crystalline mass which consists in triturating with the said mass approximately 1% of asbestos fibres.

5'. A cartridge comprising a crystalline main body of oxygen carrying crystals adapted for impregnation with a liquid fuel and a proportion of asbestos fibres not ex- 1 llt ceecllling 5% intimately incorporated therewit V 6. A cartridge comprising a crystalline main body of oxygen carrying crystals adapted for impregnation with a liquid fuel and approximately 1% of asbestos fibres, intimately incorporated therewith.

7. In or for an explosive charge a cartridge packed with oxygen carrying crystals in intimate admixture with a proportion of asbestos fibres not exceeding 5%.

8. In or for an explosive charge a cartridge packed with oxygen carrying crystals in intimate admixture with approximately 1% of asbestos fibres.

In testimony whereof I have signed my name to this specification.

ALEXANDER CRUICKSHANK SCOTT. 

